Chemical: Entrix (2003) reported that, "Both imazapyr and glyphosate killed off the eelgrass canopy of both Zostera japonica
and Z. marina. These species were killed if herbicide was applied on dry specimens at low tide, although the imazapyr was more toxic. If applied with a film of water overlying the bed, then no effect was recorded. Within 12 months post-treatment, all impacted eelgrass beds had recovered."
Physical: During April 2003 in Humboldt Bay (California, USA) University of California (UC) Extension workers began removing Z. Japonica with the help of volunteers. They attempted to install sections of plastic over Z. Japonica to kill it by shading, but found that the bay's strong tides pulled the sheets away (Rushton, 2005). The author reported that digging up Z. Japonica resulted in rapid revegetation by native eelgrass Z. Marina.
Location Specific Management Information
Under the Washington Hydraulics Code, Z. japonica is protected, however little was published regarding whether managers should continue to protect it or eradicate it as other coastal states have chosen to do (but see Bando in press). Further studies of the potential impacts of the nonnative species on native ecosystems need to be conducted to aid management decisions (Pawlak 1994) (Bando in press).
Riggs (Undated) states that "Neither WDNR (Washington Department of Natural Resources) nor WDFW (Washington Department of Fish and Wildlife) see an immediate negative effect from the spread of Z. japonica and may view Z. japonica as a 'no cost' opportunity to provide additional fish habitat and improve feeding grounds for migratory waterfowl. It's not likely that Z. japonica will be classified as a noxious weed or placed on the monitor list in the near future.”
1. Baldwin, J. R., and J. R. Lovvorn. 1994. Expansion of seagrass habitat by the exotic Zostera japonica, and its use by dabbling ducks and brant in Boundary Bay, British Columbia. Marine Ecology-Progress Series. 103(1-2). 1994. 119-127.
2. Elsa, L., S. Carlisle, and T. Klinger. UNDATED. New Directions for Managing Washington State Seagrass Resources. University of Washington.
3. Entrix. 2003. Ecological Risk Assessment of the Proposed Use of the Herbicide Imazapyr to Control Invasive Cordgrass (Spartina spp.) in Estuarine Habitat Of Washington State. Washington State Department of Agriculture.
4. Fong, T. C. W. 1999. Conservation and management of Hong Kong seagrasses. Asian-Marine-Biology. 1999; 16: 109-121.
5. Hughes, A. R., K. J. Bando, L. F. Rodriguez, and S. L. Williams. 2004. Relative effects of grazers and nutrients on seagrasses: a meta-analysis approach. Marine Ecology Progress Series 282:87-99.
6. Larned, S. T. 2003. Effects of the invasive, nonindigenous seagrass Zostera japonica on nutrient fluxes between the water column and benthos in a NE Pacific estuary. Marine Ecology-Progress Series 254:69-80.
7. Lee, S. Y., C.W. Fong, and R.S.S. Wub. 2001. The effects of seagrass Zostera japonica canopy structure on associated fauna: a study using artificial seagrass units and sampling of natural beds. Journal of Experimental Marine Biology and Ecology 259:23-50
8. Posey, M. H. 1988. Community Changes Associated with the Spread of an Introduced Seagrass, Zostera japonica. Ecology. 69(4). 1988. 974-983.
9. Rushton, N. 2005. Conservationists attempt to rid bay of nonnative plants. The Eureka Reporter.
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